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Summary of Vanya Darakchieva's activities

Research

I am working on the development of novel semiconductor materials for high-frequency and power electronics. My research also focuses on developing spectroscopic techniques for studying electronic and transport properties of materials from bulk to nanoscale.

  • III-Nitrides for applications in the next generation of wireless communication, sensing, and power infrastructures. The research focuses on optimization of epitaxial design and properties of GaN and AlGaN device structures on SiC, GaN and AlN substrates by hot-wall MOVPE.  The activity covers growth of the device structures with the main aim to minimize defect densities (dislocations and background impurities), and the design of the epi-stack targeting different functionalities, e.g. power amplification, noise, and flicker-noise, switch losses, device design, etc.
  • Terahertz ellipsometry and optical Hall effect. We have developed unique THz ellipsometry and magneto-ellipsometry (optical Hall effect) instrumentation at the Terahertz Materials Analysis Center. These novel techniques makes it possible to explore electronic, transport and magnetic properties and phenomena in e.g, semiconductors, nanomaterials, organic materials, which cannot be assessed by other means. Current research efforts include application of THz to FIR ellipsometry to study 2DEG in transistor and quantum structures, 2D materials, conductive polymers, proteins and biomaterials.
  • Ultra-wide bandgap semiconductors. Main focus is put on β-Ga2O3 for applications in high-power electronic devices with substantial efficiency gain in e.g., generation and transmission of electric power, electrification of vehicles and motor drivers.  Current research efforts include development of MOVPE of β-Ga2O3 and profound understanding of phonon, free charge carrier and electronic properties in relation to microstructure of thin films and device heterstructures.
  • 2D materials. Current research activities include using THz ellipsometry to study, understand and optimize the transport, electronic and structural properties of e.g., epitaxial graphene grown on SiC, MAXens, and BN.

More about my research...

Therahertz to FIR ellipsometer and optical Hall effect instrument at THeMAC.

Selected publications

  • Electron effective mass in In0.33Ga0.67N determined by mid-infrared optical Hall effect
     N. Armakavicius, V. Stanishev, S. Knight, P. Kühne, M. Schubert, and V. Darakchieva
    Applied Physics Letters 112, 082103 (2018)
  • In-situ terahertz optical Hall effect measurements of ambient effects on free charge carrier properties of epitaxial graphene
    S. Knight, T. Hofmann, C. Bouhafs,  N. Armakavicius, P. Kühne, V. Stanishev, I.G. Ivanov, R. Yakimova, S. Wimer, M. Schubert, and V. Darakchieva
    Scientific Reports 7, 5151 (2017)
  • Multiscale investigation of interface properties, stacking order and decoupling of few layer graphene on C-face 4H-SiC
    C. Bouhafs,  A. A. Zakharov, I. G. Ivanov, F. Giannazzo, J. Eriksson,  V. Stanishev, P. Kühne, T. Iakimov, T. Hofmann, M. Schubert, F. Roccaforte, R. Yakimova, and V. Darakchieva
    Carbon 116, 722 (2017)
  • Assessing structural, free-charge carrier, and phonon properties of mixed-phase epitaxial films: The case of InN 
    M.-Y. Xie, M. Schubert, J. Lu, P. O. Å. Persson, V. Stanishev, C. L. Hsiao, L. C. Chen, W. J. Schaff, and V. Darakchieva
    Phys. Rev. B 90, 195306 (2014)
  • Anisotropic strain and phonon deformation potentials in GaN
    V. Darakchieva, T. Paskova, M. Schubert, H. Arwin, P. P. Paskov, B. Monemar, D. Hommel, J. Off, F. Scholz, M. Heuken, B. A. Haskell, P. T. Fini, S. J. Speck, S. Nakamura
    Physical Review B 75, 195217 (2007)

Complete list of publications...

Current supervision of students

 PhD students
  • Rosalia Delgado, main supervisor (2018 - present)
  • Alexis Papamichail, main supervisor (2018 - present)
  • Dat Tran, co-supervisor (2018 - present)
  • Hengfang Zhang, main supervisor (2017 - present)
  • Shangzhi Chen, co-supervisor (2017-present)
  • Nerijus Armakavicius, main supervisor (2014-present)
  • Ingemar Persson, co-supervisor (2014-present)

List including former students... 

Current projects and funding

  • SSF Framework grant for Strategic Research on Materials for Energy Applications: Low-defect-density III-Nitrides for green power electronics, principal investigator (2018-2022)
  • Swedish Energy Agency: Developing next-generation high-power Ga2O3 material for an energy efficient smart grid, principal investigator (2018-2021)
  • VINNOVA Competence Centre: Centre for III-nitride technology (C3NiT), principal investigator (2017-2022)
  • VR Consolidator Grant: Terahertz optical Hall effect in materials for next generation high speed and high power electronics (TeraNext), principal investigator (2017-2022)
  • SSF Research Infrastructure Fellow: Center for terahertz materials analysis, principal investigator (2016-2020)
  • SSF Future Research Leaders grant: THz ellipsometry of advanced materials for high-speed electronicsprincipal investigator (2014-2019)
  • VR Junior Researcher Grant: Taming graphene for ultra-high-speed electronics: insights from novel ellipsometry techniquesprincipal investigator (2014-2017)
     
  • ÅForsk: Terahertz Ellipsometer: the core of a new Terahertz Materials Preparation and Analysis Centerprincipal investigator (2014-2015)
     
  • Swedish Innovation Agency VINNOVA - VINNMER –  Marie Curie international qualification: THz ellipsometry and optical Hall effect: important techniques to study graphene and InNprincipal investigator (2012-2017)
     
  • VR: Free-charge carrier properties and doping mechanisms of advanced semiconductor materials for high speed and THz electronicsprincipal investigator (2011-2013)
     
  • National Science Foundation (FCT) Portugal: Free-charge carrier properties and doping mechanisms in InN-based materialsprincipal investigator (2010-2013)

Current teaching

Pedagogy courses

PhD courses

  • Semiconductor Physics I (10 credits)
  • Semiconductor Physics II (10 credits)
  • Advanced semiconductor materials (10 credits)

 


Responsible for this page: Fredrik Karlsson
Last updated: 09/21/18